Biosynthesis of potential inhibitors against tobacco mosaic virus by Bacillus licheniformis T6: L-cysteine-functionalized selenium nanoparticles

Plant viral infections pose a significant challenge to agricultural productivity, leading to substantial food crop shortages. Tobacco mosaic virus (TMV) is notoriously difficult to manage due to its high environmental persistence and resistance to conventional control measures, leading to substantial crop losses. Conventional antiviral management frequently causes phytotoxicity or adverse effects on host plant physiology, which harms the host plant. Selenium nanoparticles (SeNPs) have recently emerged as a promising choice for antiviral research due to their unusual physicochemical features and biological activity. In this study, Bacillus licheniformis T6 was used to develop L-cysteine-functionalized selenium nanoparticles (Cys-SeNPs), a potent and low-risk viral inhibitor. It was discovered that the addition of cysteine significantly enhanced the effectiveness and stability of SeNPs by decreasing the size of the particles. When the concentration reached 1.0 mmol/L, Cys-SeNPs demonstrated significant efficacy against TMV, with an 81.3% inactivation rate, a treatment rate of 88.9%, and a protection rate of 85.9%, surpassing the effectiveness of SeNPs. Additionally, physiological and biochemical analyses revealed that both SeNPs types could stimulate the expression of Nicotiana tabacum var. Xanthi nc resistance-related genes PR1a , PR1b , PR5 , PAL , COI1 , and PDF1.2 . This study highlights Cys-SeNPs' tremendous potential for increasing host resistance to TMV, providing novel insights and a theoretical underpinning for microbe-based control of plant viral infections. • Microbially-produced Cys-SeNPs eliminate chemical reductants. • Cys-SeNPs demonstrate complete absence of phytotoxicity. • Act as both potent antivirals and plant immune system boosters. • Upregulate 6 key plant defense genes to induce resistance.